Nothing about chamber pressure is truly an absolute, so guesses of "how much" isn't the point; All of the signs we use are no more than indications that the pressure is TOO HIGH, the specific level is irrelivant isn't it?
Not IMO, because if you are getting pressure signs (which may or may not actually mean pressure is too high) what do you do about them? And how do you then know pressures are low enough after you have taken action?
Yes, BUT...the issue is that the load is too hot for that case in that rifle, it's not given as an absolute. If the Norma case flows, it IS NOT a safe pressure level FOR THAT CASE!
How do you know that to be true?
If a case in use turns loose it won't matter that the same load would have been safe with a different brand case. We must be safe with what we are using, what we are not using is of no help to us!
You are equating brass flowing into the ejector port with a case that is about to let go. I have never seen any evidence that brass flowing into the ejector cutout IN A LOAD MEETING SAAMI PRESSURE SPECS is a risk factor. Granted, if you are using an extremely soft case -- perhaps one damaged by overzealous annealing -- then you are risk with any reasonable pressure level, but I have never heard of this happening with modern, unaltered factory cases.
The "very little" strength of the case" makes a lot of difference in the event. Soft cases WILL rupture or blow primer pockets sooner than harder cases. How violently a rupture occurs depends a lot on how, and how much, of the case is supported in the chamber but a soft/thin case will always give way sooner than a hard/thick one.
True, but only when SAAMI pressure levels have been grossly exceeded -- unless one is arguing that certain brands of case are not safe with SAAMI loads.
"so soft cases are just as safe and useful as hard ones."
Not even close to being true, at least not so with most rifles.
I have used "soft" cases for decades without problem. But I never exceed maximum loads and am usually well under them, as I decide upon what rifle to buy based upon my needs, ie. if I want a certain bullet to go a certain speed I buy a rifle that can do that with published loads. I don't buy a rifle of lesser ability on the assumption that I can go off on my own and make it into something it wasn't meant to be.
"a custom benchrest rifle isn't going to give any of the typical pressure signs until 85,000+ PSI.)"
Okay, that can be true. But how does that matter to those of us with common factory rifles? Or the BR guy whose rifle can handle it? And the premise of this statement seems to be in contridiction of your statement above about soft cases being is as safe as hard cases. ??
It matters primarily as an illustration that there are far too many variables in "reading pressure signs" for any of those methods to mean much. As for any contradictions, you'll have to be more specific. I don't don't see it.
"..a gun with a large extractor cutout is going to show more extrusion than one with a small, tightly fitted one."
Exactly. The one with the larger cutout IS less supported than one in a tight chamber tho. And if it turns loose, the results WILL be noticable, right?
At pressures well above specification. But is the gun with the larger extractor clearance "dangerous"? I have seen no evidence of it.
"Going by the shiny spot, an 80,000 PSI load is "safe" in the match rifle, while the 45,000 PSI load is "overpressure" in the old milsurp. Both "truths" are false."
How can that be false? If the tight rifle is handling the greater pressure but the old milsurp isn't, are we to assume loading the milsurp hotter would be safe? Or should we automatically need to load the modern rifle down to old milsurp levels? In either instance, THAT would be false!
The match rifle may or may not be able to handle 80,000 PSI. There's no real way to know, other than destructive testing. Which is exactly how it was determined that 45,000 PSI (or more, in many cases) is safe in the old milsurp. The shiny spot on the case tells us nothing about how much pressure the action can handle.
"Which brings us to measuring case heads. ... more recent testing has shown that even loads put together by experienced professionals using this technique have exceeded 70,000 or even 80,000 PSI, which exceeds SAAMI limits...reading pressure signs is synonymous with pressure guessing, with your rifle -- not to mention health -- on the line."
Correct, but so what? We aren't shooting SAAMIs, we are shooting individual arms. The original data WAS safe in the arms it was developed in and the point of testing is to determine if a load, including the case, is excessive for the weapon WE use it in, right? And those who have determined those high pressue loads are NOT excessive for their weapon seems very close to some of your own earlier arguments to the contrary! All that's what the old adage to "start low and work up only if we see no exessive pressure signs" is all about, right?
This strikes me as fairly circular: "Pressure signs are valid in individual rifles because if the individual rifles don't show any pressure signs they are safe, so pressure signs are valid."
"..the idea that the hobbyist handloader can learn more about pressure by looking at his cases than the professional ballistician .."
Now, in some 45+ years of reloading and reading a LOT of liturature on the subject, that's the first time I've ever seen that observation. NO ONE suggests we can do better than the pros. Instead, we are each doing the best we can with the tools and skills we bring to the table. So long as we can actually recognise that our load is getting too hot - and back off - we have done exactly what we need to do. We (usually) recognise that our hot loads may not be safe for others, and it's all done by "reading the signs".
It seems to me that any time someone suggests that one can safely exceed published loads through the use of pressure signs, he is indeed suggesting that the home handloader knows more about ballistics than do ballisticians.
What, or how would you suggest we do otherwise?
I have already suggested it: buy a rifle based upon your needs. If your needs exceed the cartridge's KNOWN AND PUBLISHED abilities, then buy a different rifle.
